The present invention relates to pressurized gas-operated arrangements for the delivery of predetermined amounts or doses of the molten contents of a sealed and heated storage vessel having an overflow pipe.
Various arrangements are known in which predetermined amounts of liquid metal can be delivered in doses or measured quantities by the use of gas under pressure during the delivery of the metal. Such arrangements preferably use the principle of communicating vessels.
U.S. Pat. No. 3,058,180 discloses an arrangement wherein dosed amounts of a melt can be cast. The delivery in doses is effected by lowering the melt level in a storage vessel by a certain amount per casting cycle. The lowering is effected by means of increasing gas pressure. For controlling the required amounts of gas, pyrometers are lowered as probes into the fill holes, or the weight increase of the mold during the casting is measured. With such an arrangement, the storage vessel can only be kept sealed or closed to a limited extent. This occurs because the arrangement operates on the principle of communicating vessels and therefore it is connected at the bottom to uncloseable inlet and outlet openings. Furthermore, this arrangement has the disadvantage that exact dosing is not possible because of the fluctuating movement of large amounts of metal. These movements occur due to gas pressure fluctuations or during acceleration or deceleration. Another disadvantage exists in relatively large-surfaced vessels, since the delivery of small amounts results in only a minimal lowering of the liquid level in the storage vessel. This minimal lowering can only be inaccurately measured with available measuring instruments.
An arrangement is also known from British Patent No. 1,100,475 where liquid metal is conducted from a sealed and heated storage vessel by means of gas pressure. The liquid metal flows through an overflow pipe into an open vessel from which it is delivered either for continuous feeding of injection molding machines or for the intermittent filling of molds. The controlled delivery is achieved by the opening and closing of an outlet opening in the bottom of the vessel by means of a stopper. In this manner dosed amounts of liquid metal can only be cast with limited accuracy, and further, the melt is exposed to atmospheric influences in the open stopper vessel.